The present invention relates to a method and device for conveying through a pipe a diphasic fluid of high free gas content.
In the following, reference is made, by way of non limitative example, to the application of the invention to the complete recovery of petroleum effluents from an oil producing field.
Petroleum effluents from an oil producing field often comprise a liquid and a gas phase. When the gas content reaches 10 to 20% of the liquid content, which corresponds to a high volumetric gas/oil ratio, it is not possible to increase the pressure of the gas-liquid mixture with presently available pumping equipments and it becomes necessary to separate the liquid phase from the gas phase and to process them separately.
Such separation is achieved in one or more chambers by progressively reducing the pressure of the gas-liquid mixture to atmospheric pressure. Pumps are used to increase separately the liquid pressure to force it into the pipe or pipes provided therefore. The gas phase, which is separately processed, is either burnt in flares, i.e. without power recovery, or sometimes used to produce a part of the power required for actuating the oil field equipments or reinjected into the oil containing geological formations so as to increase the efficiency of oil recovery from these formations.
The gas phase is rarely liquefied or conveyed through a separate line, since this would require very expensive investments which, up to now, appear little or not at all profitable.
Not only the gas which is simultaneously produced with the liquid phase is practically never recovered, but separation of the gas and liquid phases requires a bulky equipment, which is a serious drawback in the case of offshore oil producing fields and requires a non negligible power consumption for increasing again the gas pressure which has been reduced during the gas-liquid separation.